3-Oxatricyclo[4.2.1.04,8]nonan-2-one derivatives each having a polymerizable unsaturated group at the 5-position (i.e., 2-oxatricyclo[4.2.1.0″]nonan-3-one derivatives each having a polymerizable unsaturated group at the 9-position) and 6-oxabicyclo[3.2.11,5]octan-7-one derivatives each having a polymerizable unsaturated group at the 4-position have a hydrophobic, bulky, and stable alicyclic carbocyclic ring and a hydrophilic and hydrolyzable lactone ring and contain a polymerizable unsaturated group. They are therefore used as, for example, raw materials for coating compositions and functional polymers using their specific structural properties. There have been proposed processes for easily and conveniently preparing these compounds (e.g., Patent Documents 1 and 2). The lactone rings of these compounds are hydrolyzable with bases, but the hydrolysis proceeds not so rapidly. The compounds may not sufficiently exhibit desired functions in some uses and/or their hydrolyzed products show low solubility in water and may thereby be poor in performance and be difficult to handle. They also have insufficient solubility in organic solvents.    Patent Document 1: Japanese Unexamined Patent Application Publication (JP-A) No. 2002-193961    Patent Document 2: Japanese Unexamined Patent Application Publication (JP-A) No. 2002-212174